Chapter 15-17 Flashcards
Acids Empirically Defined
Substances that Taste sour Conduct electricity React with metals to produce hydrogen gas Turn blue litmus paper red PH ranges between zero and seven
Bases empirical definition
Are Substances that: Taste bitter Conduct electricity Feel soapy or slippery PH ranges between seven and 14
Svante Arrhenius
He offered an explanation for the difference in behaviour between acids and bases
Arrhenius theory acids
Acids produce hydrogen ions when they are dissolved in water. Asses are substances that ionize in aqueous solution to form hydrogen ions
Note: the hydrogen ions are responsible for the acidic properties of these solutions
Arrhenius Theory bases
Bases produce hydroxide ions when they are dissolved in water. Faces are substances that dissociate to form hydroxide ions in aqueous solution.
Note: the hydroxide ions are responsible for the basic properties of these solutions
Hydronium Ions
The hydrogen Ion does not exist on its own but bonds to polar water molecules.
Hydrated protons, H3O+ (aq) is called a hydronium ion
Is responsible for acidic properties
Acid Rules
Can be identified because the hydrogen ion is written first in the formula
Exception: acetic acid (CH3OOH(aq))
Acids are always given the state aqueous (aq)
Naming acids
The IUPAC name consist of three words: aqueous hydrogen and the name of the Anion Example: aqueous hydrogen chloride Classic rules to name acids: Hydrogen\_\_\_ide becomes hydro\_\_\_ic acid Hydrogen\_\_\_ate becomes \_\_\_\_\_\_\_\_\_ic acid Hydrogen\_\_\_ite becomes \_\_\_\_\_\_\_\_ous acid
Acids bases and ionic substances
To distinguish between these substances we use simple diagnostic tests
Litmus test
Used primarily to distinguish acids from bases
Red litmus turns blue if a base
Blue litmus turns red if an acid
Conductivity test
Used to determine if a solution is ionic acidic basic or if the solution is molecular
If a solution conducts electricity it is either ionic, acidic, or basic
If a solution does not conduct electricity the solution contains a molecular compound
More dissolved ions will be more conductive then a solution with fewer dissolved ions
Indicators
Substances that change colour when the acidity of the solution changes are called acid base indicators
These chemicals exist in at least two different forms each with a distinct colour
Higher and lower pH
The Lower PH form (more acidic) is denoted as HIn (aq)
The higher pH form (more basic) is In-(aq)
Common indicators
Litmus paper: red in acid, blue in base
Bromothymol blue: yellow in acid, blue in base
Phenolphthalein: clear in acid, pink/purple in base
PH paper
PH paper will give an exact pH of the substance being tested, it not only indicate acidic or basic but the actual PH
Note: you can use information from various indicators to determine the pH of an unknown sample
PH as powers of 10
Measures the relative acidity of a solution. The pH Scale is a logarithmic Scale from 0-14 that gives us an indication of the nature of solution(negatives and greater than 14 are impossible)
Decrease by a pH of 1 means a substance is 10 times more acidic than another substance
Decreases of 3 pH units means substance is 1000 times more acidic
PH calculations
pH= -log [H3O+(aq)
[H3O+(aq)]= 10^-pH
Note: Square brackets imply concentration
pH of acids bases and neutral Substances
Acids have a pH between 0 and 7(lower the pH the more acidic)
Bases have a pH between 7-14(higher the pH the more basic)
Neural Substances have pH of 7
Significant digits calculations
The number of digits following the decimal point in the pH value is equal to the number of significant digits in the hydronium ion concentration
Converting pH to hydronium ion concentration
PH to hydronium concentration of a solution the hydronium ion concentration equals 10 to the negative exponent of the pH
POH and hydroxide ion concentration
Follow the same procedures to convert between POH and hydroxide ion concentration
pOH=-log[OH-(aq)]
[OH-(aq)]=10^-pOH
significant digits POH and hydroxide ion concentration
The number of digits following the decimal point in the POH value is the same as the number of significant digits of the hydroxide ion concentration
Relationship between pH/pOH and ion concentration
Inverse relationship exist between the ion concentration in the PH or POH. The higher the hydronium ion concentration the stronger the acid and the lower the pH
The higher the hydroxide ion concentration the stronger the base and the lower the POH
**a low POH would correspond to a high pH
Convert between PH andPOH
pH + pOH =14
Explaining acids
Since the acid are in in aqueous solution the particles are constantly colliding with water Molecules. When they react with water molecules The hydronium ion forms if this forms it determines acidity
**acids are substances that react with water to produce hydronium ions
Explaining bases
According to the modified theory faces or substances that react with water to produce hydroxide ions. If the base already contains hydroxide ions a simple dissociation produces the hydroxide ions directly
Predict acid basic or neutral
Some situations it is difficult to predict whether the solution will be acidic basic or neutral. In these cases you need to be told whether it was acidic or basic or given the results of the lab test (litmus turned red)
Neutralization
Neutralization reaction is a double replacement reaction where an acid reacts with a base to produce water and a neutral substance
Modified neutralization reactions
Can now be defined as the reaction between hydronium and hydroxide ions to produce water
Strong acids
High conductivity, high rate of reaction with active metals and carbonate, low pH, I concentration of hydronium ion’s, react completely (>99%) with water to form hydronium Ions
Ex: hydrochloride acid
Weak acids
Low conductivity, lower rate of reaction with active metals and carbonate, relatively high pH compared to strong acid, lower concentration of hydronium ion’s, reacts incompletely (less than 50%) with water to form relatively few hydronium Ions
Ex: acetic acid
Strong bases
High conductivity, very high pH, high concentration of hydroxide ions, dissociate completely in solution to produce hydroxide ions
*for every 1 mol of NaOH that dissociates, 1 mil of OH- is formed
Ex: sodium hydroxide
Weak bases
Lower conductivity, pH closer to seven, lower concentration of hydroxide ions, react partially less than 50% with water to produce relatively few hydroxide ions, are either ionic or molecular compounds in their pure state
Ex: baking soda
Polyprotic acids
Contain more than one acidic hydrogen ions in their formula and react more than once with water to produce hydronium ion
(In general are weak acids)
Mono protic acids
Have only one acidic hydrogen ion in their formula and react only ones with water to produce hydronium ion
Ex: hydrogen chloride
Monoprotic bases
React only once with water to produce hydroxide ions
polyprotic bases
React more than once with water all the reactions with water are much less than 50%
( generally are weak bases, their reaction with water decreases with each successive step)
